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2405 diaphragm identification

I have a pair of 2405 - 16 ohm drivers that have aftermarket 8 ohm diaphrams in them. I have obtained 2 - NOS JBL D16R2405 diaphragms from different sources. One was in a sealed JBL box and is gold in color. It is stamped "Jan 23 1996", "2405" and it has an "SP" inside a circle stamped on it as well. The second is in an older unsealed JBL box with a 1979 ship date on the box and it is blue in color. The second (blue) is stamped "APL 1979", "33752", "2731" and it too has an "SP" inside a circle stamped on it as well. Both the "33752" and "2731" are very very faint so I could be missreading the numbers. I measured ID, OD, and Voice Coil ID and they are identical to the 2nd decial place. The thicknesses vary with the older blue at ".370" and the newer gold one at ".350" which is the only difference I can see between them aside from the color and markings. Both measure within .1 or so of 7 ohms and both of them have a hand marked little dot/line by one of the VC leads which I assume identifies polarity. I use the 2405's in a home stereo and want them matched. I believe the gold colored one in the sealed JBL box is genuine but since the blue colored one was not in a sealed box I'm not so sure about that one. Can anyone offer any insight into these diaphagms? Which post (red or black) does the marked (dot/line) lead go to? Thanks for all your help.

077

Hello
I know that some of the newer old stock 2405 diaphragms I have had
were gold and that the original era 2405 diaphragms were indeed blue.
I have a new old stock opened box, I'll get what part number are on it and
let you know.

I have seen many variations of colors on the JBL tweets - all silver, all blue, all gold, and one model that has the *inside* ring a different color ( 2403 / 076 ). ANd that's not counting the OEM variations that went to the railroad / traffic companies.

I used to save them on the wall in the shop to show clients but there were too many variations and not enough nails to hang 'em.

On the 2405 I used to see all blue - now it's all gold. If the box doesn't have a bar code it's probably blue.

If it's a sealed box don't lose sleep over it. The DCR tends to be all over the map too.

I was able to obtain another JBL 2405 diaphragm in a sealed box from the same source as the previous one so I'll be assured of a matched set. Still not sure if the blue one is an older 2405 or an 077 or exactly what it is. Is there a difference between the 2405 and 077? Thanks to all for your replies.